pq....picture for a moment, if you will, a piece of very dry wood..apply a few drops of oil to the wood and see how quickly the oil is absorbed...if you apply an oil based primer directly to that dry wood, the wood will wick the oil from the primer leaving the binder and pigment which will fail in short order...apply a liberal coat of blopentine to 'condition' 'consolidate' 'nourish' 'rehydrate' the wood...wipe off the excess oil then allow the wood to set at least overnight in a dry ventilated area (oil based products set up through oxidation (moving air)...apply a coat of oil primer followed by two coats of oil or water based paint...what is this 'bonding' primer of which you speak? we typically use ben moore penetrating oil (alkdy) primer followed by bm oil finish paints....
depending on the source, 'latex' or water based paint were first introduced in the 1940's and 1950's...lead, mercury and cadmium are used in many materials as a stabilizer...some latex paints did contain lead and mercury and cadmium as 'binder' or 'stabilizers'...i think it's good that dangerous materials are being removed from production but it does leave us with rather inferior paint if compared to those available 50 years ago...
the siding on your 90 year old home is superior to pretty much anything on the market today...best practices for an old home is to retain the historic fabric and restore rather than replace....the epa has made it difficult to find folks who are willing to work on old homes but you should be able to find someone who is sensitive to old homes and is certified in safe lead paint removal... check here for more (over the top and throught the woods) regulations regarding lead paint removal:
http://www.epa.gov/lead good luck!
...jade